What is the best solution for this UV problem?
My proposed solution:


Map the item as it is. The UV-map is bent.
In the UV-editor, manually straighten the outer edges. Using SX0 or SY0 for instance.
Select the outer edges and pin them. Toggle pinning with P.
Go back to the 3D editor and do the UV-mapping again.


The pinned vertices should stay as they were and the inside should be remapped to follow.



When you pin a vertex in the UV-editor, it is marked with a red border.